Radiator for short-wave devices



July 28, 1959 g, G SCHOLZ 2,897,494

RADIATOR FOR SHORT-WAVE DEVICES Filed June 17, 1957 INVENTOR OLE GUNNARSCP-DLZ BYW atent fiice 2,897,494 Patented July 28, 1959 RADIATOR FORSHORT-WAVE DEVICES Ole Gunnar Scholz, Hamhurg-Neugraben, Germany, as-

signor to North American Philips Company Inc, New Yorlr, N.Y., acorporation of Delaware Application June 17, 1957, Serial No. 665,890

Claims priority, application Germany June 15, 1956 6 Claims.v (.Cl.343749) The present invention relates to a short-wave radiator. Moreparticularly, the invention relates to the heating of objects and moreparticularly biological tissues by electromagnetic radiation in therange of decimeter waves, and it relates especially to radiators forthis Wavelength.

Two wavelength ranges are at present permissible for radiation therapyand other heating purposes, that is, the range of about 2400 megacyclesper second, and more recently also the range of about 450 megacycles persecond. The high frequencies permit the use of ordinary radiators, thegeometric size of which corresponds to the dimensions of the surface tobe irradiated. At the low frequencies the radiator of ordinary typebecomes much too large in size with proportional variation in itsdimensions. Furthermore, it is necessary to work in the vicinity of thecore of the field to transfer the energy of the generator to the objectwith a proper efiiciency.

The object of the invention is to provide radiators, the dimensions ofwhich are artificially reduced and which permit working in the core ofthe radiation field. According to the invention, a radiator offunnel-like section, the aperture of which is approximately equal to thehalf efiective wavelength, or the half apparent wavelength of the energyin the radiator, is loaded. and tuned by means of a series-combinationof inductive and capacitive reactances which is arranged transverselyover the aperture.

According to the invention, an attractive embodiment of very simpleconstruction has transversely directed projections which extend in thecentral surface of the radiator, parallel to the electric field vector,and the foot points of which are connected to opposing walls of theradiator with a spacing of less than half the effective wavelength. Theprojections terminate at the center of the radiator with opposing endsbent-over rectangularly. The supply line is connected to the projectionssymmetrically or asymmetrically.

In such a funnel-like radiator, it is preferable for the surfacecurrents along the wall to be suppressed by the use of a known quarterwavelength choke or a resistance layer.

In order that the invention may be more readily carried into effect, itwill now be described more fully with reference to the accompanyingdrawing, in which:

Fig. l is a schematic section of an embodiment of a radiator of thepresent invention; and

Fig. 2 shows a plan view of the embodiment of Fig. 1.

The radiator comprises a V-shaped plate 1, having at the top a planeportion 2, through which a supply line 3 extends. The dimensions are sochosen that the width of the aperture, which is preferably covered by aplate 6 of low loss dielectric material, approximately corresponds tohalf the effective Wavelength for an opening angle of about 90. It isnot necessary for the radiator to be closed at its ends by means ofwalls.

In the surface situated midway between the ends, two metal projections 4are connected to the wall, which projections are directed towards eachother and have their bent extremities 5 opposite eacli other. Thespacing between the foot points is less than half the wavelength. Thelimbs of the projections 4, which are parallel to the plane of theaperture, constitute inductive reactances'. A capacitive reactance isproduced between the bent extremities 5. The radiator is tuned by meansof the two inductive reactances and the capacitive reactance. The supplyline 3 for the high frequencies is asymmetrically connected to one ofthe projections 4 at a point such that matching is obtained. Tuning andmatching vary during the operation of the radiator, since in front ofthe aperture, in the field present there, a body of variable electricalproperties is arranged. The radiator can thus be tuned and matched onlyfor a mean irradiation distance. Tuning is effected in a simple mannerby moving the bent extremities 5 of the projections 4 towards each otheror apart from each other by means of a suitable instrument made ofdielectric material. The length of one projection may also be variable,for example if a slidable shoe 5' is provided on this part.

By means. of spacers (not shown), the detuning or reflection on thesurface to be irradiated may be prevented from becoming unduly great.

In order to avoid surface currents along the outer wall of the radiator,M4 wavelength chokes 7 of known type are arranged in parallel with theinclined surfaces.

The. invention is also advantageously applicable to radiators. having acircular aperture, such as spherical or parabolic radiators.

There is. a transition range between the transfer of energy to. objectsby means of radiation and the methods by which the object is placedeither between electrodes in the condenser field or in the inductionfield produced by a coil. The condenser field may be highly homogeneous,so. that the electric lines of force penetrate the various' tissuelayers substantially at right angles. Fatter layers offer the highestresistance to this penetration and are thus heated strongest. During theinductive treatment, the electric field coupled to the induction linesis directed substantially in parallel to the tissue layers. Since thefield is non-homogeneous in this case, the skin tissue is stronglyloaded. The radiation obtained by means of a short-wave radiator may bemade homogeneous by means of effective beaming. The electric field linesthen also extend in parallel with the tissue layers, so that thisapplication permits the obtaining of optimum results in therapy.

While the invention has been described by means of a specific exampleand in a specific embodiment, I do not wish to be limited thereto, forobvious modifications will occur to those skilled in the art withoutdeparting from the spirit and scope of the invention.

What is claimed is:

1. A radiator for short-wave devices, comprsing a funnel-like sectionhaving sides forming a relatively small cross-section at one end and arelatively large crosssection aperture at the other end, said aperturehaving a width substantially equal to the half wavelength of energy insaid radiator, and means for loading and tuning said radiator aifixed toopposing sides of said section and extending substantially transverselyacross said aperture.

2. A radiator for short-wave devices, comprising a funnel-like sectionhaving sides forming a relatively small cross-section at one end and arelatively large cross section aperture at the other end, said aperturehaving a width substantially equal to the half wavelength of energy insaid radiator, and means for loading and tuning said radiator, saidlast-mentioned means comprising a series combination of inductive andcapacitive reactances affixed to opposing sides of said section andextending substantially transversely across said aperture.

3. A radiator for short-wave devices, comprising a funnel-like sectionhaving sides forming a relatively small cross-section at one end and arelatively large cross-section aperture at the other end, said aperturehaving a Width substantially equal to the half Wavelength of energy insaid radiator, means for loading and tuning said radiator, saidlast-mentioned means comprising a pair of projections affixed toopposing sides of said section and extending substantially transverselyacross said aperture, the side ends of said projections being separatedfrom each other by a distance less than the half wavelength of energy insaid radiator and the inner ends of said projections being bent to formsubstantially parallel arms in relatively close proximity to each other,said projections extending substantially parallel to the electric fieldvector of said radiator, and means for applying input electrical energyto at least one of said projections.

4. A radiator for short-wave devices, comprising a funnel-like sectionhaving sides forming a relatively small cross-section at one end and arelatively large crosssection aperture at the other end, said aperturehaving a width substantially equal to the half wavelength of energy insaid radiator, means for loading and tuning said radiator, saidlast-mentioned means comprising a pair of projections aflixed toopposing sides of said section and extending substantially transverselyacross said aperture, the side ends of said projections being separatedfrom each other by a distance less than the half wavelength of energy insaid radiator and the inner ends of said projections being bent to formsubstantially parallel arms in relatively close proximity to each other,said projections extending substantially parallel to the electric fieldvector of said radiator, means for varying the separation between saidarms, and means for applying input electrical energy to at least one ofsaid projections.

5. A radiator for short-wave devices, comprising a funnel-like sectionhaving sides forming a relatively small cross-section at one end and arelatively large crosssection aperture at the other end, said aperturehaving a width substantially equal to the half wavelength of energy insaid radiator, means for loading and tuning said radiator, saidlast-mentioned means comprising a pair of projections afiixed toopposing sides of said section and extending substantially transverselyacross said aperture, the side ends of said projections being separatedfrom each other by a distance less than the half wavelength of energy insaid radiator and the inner ends of said projections being bent to formsubstantially parallel arms in relatively close proximity to each other,said projections extending substantially parallel to the electric fieldvector of said radiator, means for varying the separation between saidarms, means for applying input electrical energy to at least one of saidprojections, and means for damping surface currents on the outersurfaces of said sides.

6. A radiator for short-wave devices, comprising a funnel-like sectionhaving sides forming a relatively small cross-section at one end and arelatively large cross-section aperture at the other end, said aperturehaving a width substantially equal to the half wavelength of energy insaid radiator, means for loading and tuning said radiator, saidlast-mentioned means comprising a pair of projections afiixed to and inelectrically conductive connection with opposing sides of said sectionand extending substantially transversely across said aperture, the sideends of said projections being separated from each other by a distanceless than the half wavelength of energy in said radiator and the innerends of said projections being bent to form substantially parallel armsin relatively close proximity to each other, said projections extendingsubstantially parallel to the electric field vector of said radiator,and means for applying input electrical energy to at least one of saidprojections.

References Cited in the file of this patent UNITED STATES PATENTS2,307,012 Barrow Jan. 5, 1943 2,403,909 Carter July 16, 1946 2,627,571Hiehle et al. Feb. 3, 1953 2,716,694 Schroeder Aug. 30, 1955 2,828,486Scheldorf Mar. 25, 1958 FOREIGN PATENTS 616,996 Great Britain Jan. 31,1949

